Perforated retroreflective film

ABSTRACT

A see-through retroreflective structure includes a transparent polymeric film, an array of retroreflective elements attached to the polymeric film, and an array of apertures through the retroreflective structure within the array of retroreflective elements. In one embodiment, the retroreflective structure includes a metalized reflective layer formed on the transparent prism elements and a support layer, such as a fabric, is attached to the metalized reflective layer.  
     The method includes providing a transparent polymeric film. An array of retroreflective elements is attached to the polymeric film. The array of retroreflective elements and the transparent polymeric film are perforated through the retroreflective structure to form an array of apertures, thereby forming a retroreflective structure. The apertures are of sufficient size and spacing to provide a see-through capability. In one embodiment, a metalized reflective layer can be applied to the retroreflective elements and a support layer, such as a fabric, is attached to the metalized reflective layer.

RELATED APPLICATIONS

[0001] This application is a Continuation-in-Part Application of U.S.application Ser. No. 09/211,962, filed Dec. 15, 1998, which claims thebenefit of U.S. Provisional application Ser. No. 60/069,818, filed Dec.16, 1997. The contents of each application are incorporated herein byreference in their entirety.

BACKGROUND OF THE INVENTION

[0002] Retroreflective materials are employed for various safety anddecorative purposes. Particularly, these materials are useful at nighttime when visibility is important under low light conditions. Withperfect retroreflective materials, light rays are reflected essentiallytowards a light source in a substantially parallel path along an axis ofretroreflectivity.

[0003] Many types of retroreflective material exist for variouspurposes. These retroreflective materials can be used as reflectivetapes and patches for clothing, such as vests and belts. Also,retroreflective materials can be used on posts, barrels, traffic conecollars, highway signs, warning reflectors, etc. Retroreflectivematerial can be comprised of arrays of randomly oriented micron diameterspheres or close packed cube-corner (prismatic) arrays.

[0004] Cube-corner or prismatic retroreflectors are described in U.S.Pat. No. 3,712,706, issued to Stamm on Jan. 23, 1973, the teachings ofwhich are incorporated by reference herein. Generally, the prisms aremade by forming a master negative die on a flat surface of a metal plateor other suitable material. To form the cube-corners, three series ofparallel equidistance intersecting V-shaped grooves 60 degrees apart areinscribed in the flat plate. The die is then used to process the desiredcube-corner array into a rigid flat plastic surface.

[0005] Further details concerning the structures and operation ofcube-corner microprisms can be found in U.S. Pat. No. 3,684,348, issuedto Rowland on Aug. 15, 1972, the teachings of which are incorporated byreference herein. A method for making retroreflective sheeting is alsodisclosed in U.S. Pat. No. 3,689,346, issued to Rowland on Sep. 5, 1972,the teachings of which are incorporated by reference herein. Thedisclosed method is for forming cube-corner microprisms in acooperatively configured mold. The prisms are bonded to sheeting whichis applied thereover to provide a composite structure in which thecube-corner formations project from one surface of the sheeting.

SUMMARY OF THE INVENTION

[0006] The present invention is directed to a “see-through”retroreflective structure and a method for forming the same. Thesee-through retroreflective structure includes a transparent polymericfilm, an array of retroreflective elements attached to the polymericfilm, and an array of apertures through the retroreflective structurewithin the array of retroreflective elements. In one embodiment, theretroreflective structure includes a metalized reflective layer formedon the retroreflective elements and a support layer, such as a fabric,is attached to the metalized reflective layer. The see-through featureof the structure allows a person inside a vehicle or building to see outa window while those viewing outside can see a graphic display on thestructure during the day and night.

[0007] A retroreflective structure is also provided which includes afilm having a first side and a second side, a first array ofretroreflective cube-corner elements attached to the first side of thefilm, and an array of apertures through the retroreflective structurewithin the array of retroreflective cube-corner elements. A second arrayof retroreflective cube-corner elements is attached to the second sideof the film. The apertures can be formed by removing a portion of thefilm and the elements.

[0008] The method includes attaching an array of retroreflectiveelements on a transparent polymeric film. The array of retroreflectiveelements and the transparent polymeric film are perforated through theretroreflective structure to form an array of apertures, thereby forminga see-through retroreflective structure. In one embodiment, a metalizedreflective layer can be applied to the retroreflective elements and asupport layer, such as a fabric, is attached to the metalized reflectivelayer.

[0009] A retroreflective particle is further provided comprising a filmhaving a first side and a second side, a first array of retroreflectivecube-corner elements attached to the first side of the film, and asecond array of retroreflective cube-corner elements attached to thesecond side of the film.

[0010] A transflector is also provided which includes a film, an arrayof retroreflective cube-corner elements attached to a first side of thefilm, an array of apertures through the retroreflective structure withinthe array of retroreflective cube-corner elements, and a printed sheetattached to a second side of the film. In one embodiment, the aperturesare formed by removing a portion of the film and the elements. A diffusefilm can be attached to the metalized reflective layer.

[0011] The present invention can be used as trim on clothing apparel,such as running suits and running shoes. In particular, the inventioncan display a moiré pattern. Also, the invention can be used on windowsto partially retroreflect incoming light while allowing a person topartially see through the window from the other side. Further, theinvention can be used as advertising display panels on windows, asreflective sun screens for windows in automobiles, etc. Furthermore, thestructure is suitable for ink jet and digital printing with a whitenessbackground.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a cross-sectional view of a first embodiment of aretroreflective structure of the present invention.

[0013]FIG. 2 is a top view of the first embodiment of a retroreflectivestructure of the present invention.

[0014]FIG. 3 is a cross-sectional view of a second embodiment of theretroreflective structure of the present invention.

[0015]FIG. 4 is a schematic diagram of a second embodiment of the methodfor forming the invention.

[0016]FIG. 5 is a cross-sectional view of a method for forming analternative retroreflective structure at a first point in forming athird embodiment of the present invention.

[0017]FIG. 6 is a cross-sectional view of a method for forming analternative retroreflective structure at a second point in forming thethird embodiment of the present invention.

[0018]FIG. 7 is a cross-sectional view of a method for forming analternative retroreflective structure at a first point in forming afourth embodiment of the present invention.

[0019]FIG. 8 is a cross-sectional view of a method for forming analternative retroreflective structure at a second point in forming thefourth embodiment of the present invention.

[0020]FIG. 9 is a cross-sectional view of a method for forming analternative retroreflective structure at a point in forming a fifthembodiment of the present invention.

[0021]FIG. 10 is a cross-sectional view of a method for forming analternative retroreflective structure at a point in forming a sixthembodiment of the present invention.

[0022]FIG. 11 is a cross-sectional view of a method for forming analternative retroreflective structure at a second point in forming thesixth embodiment of the present invention.

[0023]FIG. 12 is a cross-sectional view of a method for forming analternative retroreflective structure at a first point in forming aseventh embodiment of the present invention.

[0024]FIG. 13 is a cross-sectional view of a method for forming analternative retroreflective structure at a second point in forming theseventh embodiment of the present invention.

[0025]FIG. 14 is a cross-sectional view of a method for forming analternative retroreflective structure at a third point in forming theseventh embodiment of the present invention.

[0026]FIG. 15 is a cross-sectional view of a method for forming analternative retroreflective structure at a point in forming an eighthembodiment of the present invention.

[0027]FIG. 16 is a cross-sectional view of another embodiment of aretroreflective structure of the present invention.

[0028]FIG. 17 is a cross-sectional view of yet another embodiment of theretroreflective structure of the present invention.

[0029]FIG. 18 is a cross-sectional view of another embodiment of theretroreflective structure of the present invention.

[0030]FIG. 19 is a cross-sectional view of yet another embodiment of theretroreflective structure of the present invention.

[0031]FIG. 20 is a cross-sectional view of a further embodiment of theretroreflective structure of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0032] The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention. All percentages and parts are by weightunless otherwise indicated.

[0033] Retroreflective structure 10, as shown in FIG. 1, has a base film12 that is comprised of a transparent thermoplastic film, such aspolyvinyl chloride, polyvinylidene chloride, urethane films,polyfluorocarbon polymers, etc. In another embodiment, the thermoplasticis an ethylene-tetrafluoroethylene copolymer. In alternativeembodiments, the base film 12 can be formed from an elastic material,such as flexible polyether urethanes which perform well in launderingand flexible polyaliphatic urethanes which perform well in outdoorenvironments. Base film 12 is transparent to visible light and can beeither clear or colored. An example of a suitable base film 12 is apolyvinyl chloride film available from Renoliot Corp. under thetrademark Renoliot™ H1W series. Base film 12 can have a thickness in therange of between about 0.001 and 0.022 inches (0.025 and 0.56 mm). In apreferred embodiment, the thickness is in the range of between about0.008 and 0.02 inches (0.2 and 0.51 mm). The selected thickness isdependent upon the method of fabrication, such as heating, radio highfrequency welding, ultrasonic welding, the thermoplastic selected, andthe characteristics desired for the retroreflective structure.

[0034] The prism array 14, which can include retroreflective cube-cornerprism elements 16, is formed on the base film 12. Prism array 14 has awindow side 18 exposed to incoming rays R and facet sides 20 and isattached on window side 18 to the base film 12. Prism array 14 is formedof a transparent polymer. After being formed, the polymer is preferablyrigid at room temperature, which is defined as being substantiallyinflexible. The rigidity of the polymer in the prism array allows theprism elements to retain their optical characteristics. The prism arraypolymer can also be non-extensible, which is defined as not beingcapable of being substantially stretched without breaking. The polymeris selected from a wide variety of polymers which include the polymersof urethane, acrylic acid esters, cellulose esters, ethylenicallyunsaturated nitriles, hard epoxy acrylates, etc. Other polymers includepolycarbonates, polyesters and polyolefins, acrylated silanes, hardpolyester urethane acrylates. Other polymers which are not as rigid canalso be used. These include polyvinyl chloride and polyvinylidenechloride. Preferably, the polymer is cast in a prismatic mold with amonomer or oligomer polymerization initiated by ultraviolet radiation.

[0035] The prism elements 16 of the prism array 14 can be cube-corner inshape and have a length along each cube-side edge in the range ofbetween about 0.0015 and 0.02 inches (0.038 and 0.51 mm). In oneembodiment, each cube-side edge has a length of about 0.006 inches (0.15mm). Preferably, each cube-side edge has a length of between about 0.004and 0.008 inches (0.1 and 0.2 mm).

[0036] The thickness of prism array 14 at valley 22, where the rigidprism elements intersect, is preferably sufficiently thin so that theprism array 14 can crack and split along the valleys 22 when a minimalforce is applied to retroreflective structure 10. In one embodiment, thethickness of prism array 14, which is the distance from window side 18to apex 21 of prisms, is in the range of between about 0.002 and 0.009inches (0.05 and 0.23 mm).

[0037] The base film 12 provides a substrate for prism array 14 toprovide a smooth surface upon which the prism elements can be attached.The window side 18 of the prism elements 16 is attached to the base film12. The prism array 14 can be laminated to the base film 12 with atransparent adhesive. Alternatively, the prism array 14 can be castdirectly onto the base film 12.

[0038] An adhesive 24 can be applied to the prism facets 20 forattaching a backing layer to the retroreflective structure. If anadhesive is employed on the prism facets, the adhesive can cause thesurface of the prisms to wet, thereby destroying the air interface andeliminating the ability of the prism to retroreflect. As a result,reflective coating 26 is preferably deposited on the surface of thedihedral facets 20. Typically, the reflective coatings are formed bysputtering aluminum, silver or gold or by vacuum metalization.Alternatively, metal lacquers, dielectric coatings and other specularcoating materials can be employed.

[0039] Backing layer 28 is placed on the facet side 20 of the prismarray 14. The backing layer 28 can be formed of a thermoplastic. Forinstance, backing film 28 can be formed from a thermoplastic, such as apolyvinyl chloride, polyvinylidene chloride, urethane films,polyfluorocarbon polymers including an ethylene-tetrafluoroethylenecopolymer, etc., which has a low temperature of distortion. Thethermoplastic of backing layer 28 can be transparent to visible lightand is either clear or colored. Alternatively, backing layer 28 can be acloth or fabric, such as a polyester cloth. In one embodiment, the basefilm 12 and backing layer 28 both include polyvinyl chloride. Inalternative embodiments, the backing layer 28 can be formed from anelastic material, such as flexible polyether or polyaliphatic urethanesor fabrics with built in elastic fibers, which can be formed fromurethane or rubber materials. Backing layer 24 can have a thickness inthe range of between about 0.005 and 0.02 inches (0.12 and 0.51 mm).

[0040] In accordance with the invention, a plurality of apertures 30 areformed in retroreflective sheeting 10 and extend through the thicknessof retroreflective structure 10. The apertures are of sufficient sizeand spacing from one another to allow the average person to see throughthe otherwise opaque structure. The apertures 30 can be formed, such asby punching holes in the structure using a suitable tool of variousshapes including circles, ovals, rectangles, squares, etc. Also, theapertures can be in the shape of letters or a logo. Apertures 30 can beuniformly or randomly arranged in an array on the structure. Typically,the apertures 30 can be circles having a diameter in the range ofbetween about 0.25 and 0.75 inches (6.35 and 19.05 mm). The array ofapertures can cover about 50 percent of the surface area of theretroreflective structure. The apertures provide breathability to thestructure. The retroreflective structure, when superimposed over anotherperforated structure, can result in a moiré effect. Such configurationscan be incorporated into clothing or footwear to provide a decorativepattern while providing retroreflectivity for safety.

[0041] The base film and prism array portion of one embodiment of theretroreflective structure 10 can be formed by one of the methodsdisclosed in U.S. Pat. No. 3,684,348, issued to Rowland on Aug. 15,1972; U.S. Pat. No. 3,689,346, issued to Rowland on Sep. 5, 1972; U.S.Pat. No. 3,811,983, issued to Rowland on May 21, 1974; U.S. Pat. No.3,830,682, issued to Rowland on Aug. 20, 1974; U.S. Pat. No. 3,975,083,issued to Rowland on Aug. 17, 1976; U.S. Pat. No. 4,332,847, issued toRowland on Jun. 1, 1982; U.S. Pat. No. 4,801,193, issued to Martin onJan. 31, 1989; U.S. Pat. No. 5,229,882, issued to Rowland on Jul. 20,1993; U.S. Pat. No. 5,236,751, issued to Martin et al. on Aug. 17, 1993;U.S. Pat. No. 5,264,063, issued to Martin on Nov. 23, 1992; U.S. Pat.No. 5,376,431, issued to Rowland on Dec. 27, 1994; U.S. Pat. No.5,491,586, issued to Phillips on Feb. 13, 1996; U.S. Pat. No. 5,512,219,issued to Rowland on Apr. 30, 1996; U.S. Pat. No. 5,558,740, issued toBernard et al. on Sep. 24, 1996; U.S. Pat. No. 5,592,330, issued toBernard on Jan. 7, 1997; and U.S. Pat. No. 5,637,173, issued to Martinet al. on Jun. 10, 1997. The teachings of each patent are incorporatedherein by reference.

[0042] In one embodiment, a six mil (0.15 mm) polyvinyl chloride film islaminated to a two mil (0.05 mm) polyethylene terepthalate (PET)carrier. The polyvinyl chloride film is tie coated and retroreflectiveprisms are cast on the tie coated polyvinyl chloride film. Theretroreflective prisms are metalized. The metalized layer may or may notneed to be protected by a coating of some type depending on theapplication requirements. In embodiments where a silver appearance ofmetalization is not preferred, a color (either the same color as the topsurface or another) can be printed or coated on the metalized layer. Atop view of the retroreflective structure is shown in FIG. 2.

[0043] Referring now to FIG. 4, a preferred method of forming theinvention will now be described in further detail. A metalizedretroreflective structure film 100, formed as described above, isunwound from roll 102 and directed to a device 104, such as a step andrepeat die punch system, for punching apertures in retroreflectivestructure film 100. The metalized retroreflective structure film 100 iswound up at windup station 106. The punched particles 50 ofretroreflective film described in detail above and shown in FIG. 3 droponto auto platen 105 and are collected from platen 105. Alternatively,as shown in FIG. 4, the particles 50 can be directly applied from device104 to an adhesive coated substrate 110, such as a fabric, which isunwound from fabric roll 112, as shown in FIG. 4. Particles 50 can alsobe dispersed onto the adhesive side 113 of the adhesive coated substrate110 from particle dispenser 114. Pinch rollers 116 press the particlesagainst adhesive coated substrate 110. Any loose particles are caught intray 118 as the adhesive coated substrate and particles exit pinchrollers 116. Top film 122 is unrolled from top film roller 124 and islaminated to adhesive coated substrate with particles in between the twolayers by laminating rollers 126. The laminated structure 127 is woundup on windup roller 128.

[0044] The particles are suitable for use as decorative or conspicuityparticles on clothing, T-shirt signs, pavement marking lines, trafficsigns, bicycle helmets, tarpaulins, etc. The particles can be mixed in agel and applied to a substrate.

[0045] For use in low temperature processes (below the meltingtemperature of PET or polyvinyl chloride), the particles stay intactwithin the plastic substrate during lamination. For use where thepolymer processing temperature exceeds the melting point of PET, thefilm deforms but the thermoset prisms and/or reflective coating remainsintact.

[0046] In another embodiment, the perforated retroreflective structurecan be applied to the inside of a window. Shown in FIG. 5, polyvinylfilm 140 is laminated to a carrier film 142, and the polyvinyl film 140is coated with tie coat 144. Prisms 146 are cast on the tie coat 144 andthe prisms are silver metalized. The structure is perforated with astamping device to form aperture 150. A barrier film 152, such as paperor polypropylene, is added to the metalized side 148 with an adhesive151 to provide dimensional stiffness and allows the film to be ink jetprinted. Shown in FIG. 6, the carrier film is removed and the polyvinylfilm is either screen printed or ink jet printed using plasticol inks154. By using such inks, the surface of the polyvinyl film 140 has astatic cling property, thereby allowing the structure to be applied onthe inside of a window 156. Screen printing is a preferred embodimentfor long runs or ultraviolet light resistant applications. In anotherembodiment, a PET film can be used for the top layer for printing on. Inyet another embodiment, a dye receptive film can be formed on orattached to the polyvinyl film 140 for reception of inks and the like.

[0047] The perforated retroreflective structure can be applied to theoutside of a window. Shown in FIG. 7, a method for forming the structureincludes applying a tie coat 160 to PET film 162. Prisms 164 are cast onthe tie coat 160 and then metalized to form metalized layer 166. Themetalized prisms are coated with a removable acrylic-based adhesive 168,preferably with a black pigment incorporated therein, and a siliconecoated paper release liner is applied to the acrylic-based adhesive. Thefilm is perforated with a perforator to form aperture 172. A barrierfilm 174, such as paper or polypropylene, is attached to the releaseliner 170 to provide additional dimensional stiffness. The film can thenbe printed on the exposed PET side with screening 176, ink jet printingor another suitable method. Ink jet printers can be a pigmented solventsystem that can offer ultraviolet light resistance for about twelvemonths. As shown in FIG. 8, the temporary release liner 170 is removedand the retroreflective structure can be attached to the outside of awindow 180.

[0048] In another embodiment, shown in FIG. 9, a polyvinyl film can belaminated to a carrier film, such as a two mil (0.05 mm) PET film 162,and then the polyvinyl film 182 is tie coated. Retroreflective prismelements are cast on the tie coat 160 and then are metalized. Themetalized prisms are coated and the carrier film is printed on by asimilar step as discussed in the prior paragraph. The structure can beapplied to the outside of a window.

[0049] A transflector material for use in airport signs is typicallyback lit, but it needs to be retroreflective in the event of a poweroutage. In one embodiment, the transflector material, shown in FIG. 10,is formed by laminating a polyvinyl film 200 to a carrier film 202, suchas PET, and the polyvinyl film is coated with a tie coat 206. Prisms 208are cast on the tie coat 206. The prisms 208 are metalized with metallayer 210. The film is perforated to form apertures 212. The perforatedfilm is laminated to a white diffuse film 214. Shown in FIG. 11, thecarrier film is then removed from the vinyl film. A transparent adhesive216 is applied to the polyvinyl film, and the film is applied to a silkscreen-type printed sheet 218 of transparent material for use in a sign.The printed sheet 218 can be formed from polyvinyl chloride, polymethylmethacrylate (PMMA), or other suitable materials. A coating can beprovided over the printed sheet 218 for purposes such as preventingabrasions to the printed sheet.

[0050] A seamless graphic film 220, as shown in FIG. 12, can be formedto hide or remove seam lines created by a mold. The seam lines 222 areremoved by cutting out as much of the seam lines as possible andreplacing them with glass beads 224. A polyvinyl prismatic internalreflective element film 226 with prisms 228 laminated with a PET carrierfilm 232 is perforated to form apertures 234. The PET carrier film 232is removed from the perforated vinyl prismatic film 226. The perforatedretroreflective prismatic film 226 is coated with a light tack removableadhesive so that the reflective surface (window surface) is in contactwith the adhesive. Beads 224, preferably high refractive index glassbeads, are coated on the film 220. In FIG. 13, the beads 224 attachwhere the beads are exposed to the adhesive 236 in the apertures 234 ofthe vinyl prismatic film 220. The facets of the prisms 228 and theattached beads are metalized with metalized layer 230. In anotherembodiment, metalized one or two sided corner cube chips or particlesmay be bonded to the exposed adhesive to provide additionalretroreflective area, glitter effects, and/or color effects. Theparticles can also include metalized “open-face” cube-corner prisms,such as taught in U.S. Application Ser. No. 09/488,129, filed Jan. 20,2000, the teachings of which are incorporated herein by reference. Thecorner cubes may be of a different size than the corner cubes formed onthe film 226.

[0051] As shown in FIG. 14, base adhesive 238, preferably a whiteadhesive, and a backing film 240 are applied to the metalized layer 230.The low-tack adhesive 236 is removed and the film is coated with aflexible transparent weatherable ink receptive system 242. The formedstructure provides a balanced set of properties with good narrowobservation for long distance sight detection and with good angularityfor viewing at short distances.

[0052] In another embodiment, as shown in FIG. 15, a flexible filmhaving prisms 252 cast on a tie coat 253 and metalized layer 254 on thefacets of the prisms is perforated to form apertures 256. The perforatedfilm is laminated using an adhesive 257 to a fabric backed material 258.The film is then extrusion coated with a clear abrasion and ultravioletlight resistant material 260, such as polyvinyl chloride orpolyurethane. In another embodiment, prior to lamination, colored PETglitter pieces 262 are coated onto the surface of perforated film whichattaches to the areas where the adhesive is present in the perforationsto provide a partially glitter-coated perforated reflective film.

[0053] Often white ultraviolet curable ink, either on the facets of theprisms or in the tie coat on the window side of the prisms, is used toachieve the necessary Cap Y to meet industry whiteness specifications.While the white printing enhances the Cap Y performance, it alsodestroys the retroreflectivity of the prisms it covers, therebyeffectively destroying sometimes about thirty percent of theretroreflectivity. The white printing can be in the form of a logo,lettering, etc. In addition, the step of printing can expose theprismatic film to excessive heat which can negatively impact theresulting retroreflectivity. Further, printing on the tie coat reducesthe run speeds because of the difficulty in curing the prisms.

[0054]FIG. 16 illustrates another embodiment of a retroreflectivestructure 10′ in accordance with the invention. This embodiment issimilar to the embodiment of FIG. 1 but further includes a second prismarray 14′, which is formed on the base film 12′, attached to a secondside of the layer 28. Thus, light rays R are retroreflected from bothsides of the structure 10′. As in other embodiments, a plurality ofapertures 30 are formed in the retroreflective sheeting 10′. The punchedparticles 51′ from apertures 30, as shown in FIG. 17, can be used fordecorative or conspicuity purposes.

[0055]FIG. 18 illustrate another embodiment of a retroreflectivestructure which includes a second base film 12′ having a prism array14′. This arrangement provides additional retroreflectivity in theaperture 30 area. The prism array 14′ can further include a reflectivecoating deposited on the surface of the dihedral facets 20′. Further,backing layer 28 can be attached to the prism area 14′. FIG. 19 issimilar to FIG. 18 and further includes backing layer 28 disposedbetween the prism arrays 14 and 14′.

[0056]FIG. 20 illustrates a further embodiment of a retroreflectivestructure in which the prism array 14′ and base film 12′ as disposed onthe top side of the film. In one embodiment, the prism array 14′ isbonded to the base film 12 by a substantially clear adhesive 15. Theprisms suspended over the apertures 30 are air-backed and provideretroreflection at the apertures. The remaining prisms are “wetted-out”by the adhesive 15 and do not provide retroreflection.

EQUIVALENTS

[0057] While this invention has been particularly shown and describedwith references to preferred embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the spirit and scope of theinvention as defined by the appended claims. Those skilled in the artwill recognize or be able to ascertain using no more than routineexperimentation, many equivalents to the specific embodiments of theinvention described specifically herein. Such equivalents are intendedto be encompassed in the scope of the claims.

What is claimed is:
 1. A retroreflective structure comprising: a) a filmhaving a first side and a second side; b) a first array ofretroreflective cube-corner elements attached to the first side of thefilm; and c) an array of apertures through the retroreflective structurewithin the array of retroreflective cube-corner elements, the aperturesformed by removing a portion of the film and the elements.
 2. Theretroreflective structure of claim 1 further comprising a second arrayof retroreflective cube-corner elements attached to the second side ofthe film.
 3. The retroreflective structure of claim 2 wherein theretroreflective cube-corner elements of the first array and the secondarray of retroreflective cube-corner elements include a metalizedreflective layer.
 4. The retroreflective structure of claim 1 whereinboth sides of the film retroreflect incoming light.
 5. Theretroreflective structure of claim 1 further comprising a first polymerlayer attached to the first array of retroreflective cube-cornerelements and a second polymer layer attached to the second array ofretroreflective cube-corner prisms.
 6. The retroreflective structure ofclaim 5 wherein the first polymer layer and the second polymer layerinclude a transparent polymer.
 7. The retroreflective structure of claim1 further comprising a polymer layer attached to the first array ofretroreflective cube-corner elements and a barrier film covering atleast some of the apertures for providing stiffness to theretroreflective structure while an ink or paint is applied to thepolymer layer.
 8. The retroreflective structure of claim 1 wherein theretroreflective structure is attached to a window.
 9. Theretroreflective structure of claim 8 further comprising an adhesivedisposed between the cube-corner elements and an outer surface of thewindow.
 10. The retroreflective structure of claim 1 further comprisinga polyvinyl film attached to the first array of retroreflectivecube-corner elements and further comprising a carrier film disposed onthe polyvinyl film opposite the cube-corner elements.
 11. Theretroreflective structure of claim 10 further comprising an ink or paintapplied to the carrier film.
 12. The retroreflective structure of claim11 wherein the retroreflective structure is applied to an outer surfaceof a window.
 13. The retroreflective structure of claim 1 furthercomprising a polymer layer attached to the first array ofretroreflective cube-corner elements, wherein an ink or paint applied tothe polymer layer.
 14. The retroreflective structure of claim 13 whereinthe retroreflective structure is attached to an inner surface of awindow.
 15. A retroreflective particle comprising: a) a film having afirst side and a second side; b) a first array of retroreflectivecube-corner elements attached to the first side of the film; and c) asecond array of retroreflective cube-corner elements attached to thesecond side of the film.
 16. The retroreflective particle of claim 15wherein a plurality of the retroreflective particles are attached to anadhesive coated substrate.
 17. The retroreflective particle of claim 16wherein a top film is laminated over the retroreflective particles onthe adhesive coated substrate.
 18. The retroreflective particle of claim15 , wherein the retroreflective particles are mixed with a gel.
 19. Amethod for forming a retroreflective structure, comprising: a) providinga film having a first side and a second side; b) attaching a first arrayof retroreflective cube-corner elements to the first side of the film;and c) perforating the array of retroreflective cube-corner elements andthe film to remove a portion of the retroreflective cube-corner elementsand the film to form an array of apertures through the retroreflectivestructure.
 20. The method of claim 19 further comprising the step ofattaching a second array of retroreflective cube-corner elements to thesecond side of the film.
 21. The method of claim 19 wherein the array ofretroreflective cube-corner elements is made retroreflective by applyinga metalized reflective layer to the array of prismatic elements.
 22. Themethod of claim 19 further including the step of: d) collectingretroreflective particles formed by perforating the array ofretroreflective elements and the film.
 23. A transflector comprising: a)a film; b) an array of retroreflective cube-corner elements attached toa first side of the film; c) an array of apertures through theretroreflective structure within the array of retroreflectivecube-corner elements, the apertures formed by removing a portion of thefilm and the elements; and d) a printed sheet attached to a second sideof the film.
 24. The transflector of claim 23 wherein theretroreflective cube-corner elements include a metalized reflectivelayer.
 25. The transflector of claim 23 wherein a diffuse film isattached to the metalized reflective layer.
 26. A retroreflectivestructure comprising: a) a film; b) an array of retroreflectivecube-corner elements attached to the film; c) an array of aperturesthrough the retroreflective structure within the array ofretroreflective cube-corner elements; and d) a plurality of beads withinthe array of apertures.
 27. The retroreflective structure of claim 26further comprising an ink receptive system disposed on the film.
 28. Theretroreflective structure of claim 26 wherein the retroreflectivecube-corner elements include a metalized reflective layer.
 29. Theretroreflective structure of claim 26 wherein the apertures are formedby removing a portion of the film and the elements.
 30. Aretroreflective structure comprising: a) a film having a first side anda second side; b) an array of retroreflective cube-corner elementsattached to the first side of the film; c) an array of apertures throughthe retroreflective structure within the array of retroreflectivecube-corner elements, the apertures formed by removing a portion of thefilm and the elements; and d) an ultraviolet light resistant layerdisposed on the second side of the film.
 31. The retroreflectivestructure of claim 30 further comprising colored polyethyleneterepthalate pieces disposed between the second side of the film and theultraviolet light resistant layer.
 32. The retroreflective structure ofclaim 32 wherein the retroreflective cube-corner elements include ametalized reflective layer.
 33. A retroreflective structure comprising:a) a film; b) an array of retroreflective cube-corner elements attachedto the film; c) an array of apertures through the retroreflectivestructure within the array of retroreflective cube-corner elements; andd) a plurality of retroreflective particles within the array ofapertures.
 34. The retroreflective structure of claim 33 wherein theretroreflective particles include a film having a first side and asecond side and a first array of retroreflective cube-corner elementsattached to the first side of the film.
 35. The retroreflectivestructure of claim 34 wherein the retroreflective particles furtherinclude a second array of retroreflective cube-corner elements attachedto the second side of the film.
 36. A retroreflective structurecomprising: a) a first film having a first side and a second side; b) afirst array of retroreflective cube-corner elements attached to thefirst side of the first film; c) an array of apertures through theretroreflective structure within the first array of retroreflectivecube-corner elements; d) a second film having a first side and a secondside, the second side being disposed adjacent to the first array ofretroreflective cube-corner elements; and e) a second array ofretroreflective cube-corner elements attached to the first side of thesecond film.
 37. The retroreflective structure of claim 36 furthercomprising a backing layer disposed between the first array ofretroreflective cube-corner elements and the second array ofretroreflective cube-corner elements.
 38. The retroreflective structureof claim 36 further comprising a backing layer attached to the secondarray of retroreflective cube-corner elements.
 39. The retroreflectivestructure of claim 36 wherein the apertures are formed by removing aportion of the film and the elements.
 40. The retroreflective structureof claim 36 wherein the second array of retroreflective cube-cornerelements is made retroreflective by applying a metalized reflectivelayer to the elements.
 41. A retroreflective structure comprising: a) afirst film having a first side and a second side; b) a first array ofretroreflective cube-corner elements attached to the first side of thefirst film; c) an array of apertures through the retroreflectivestructure within the first array of retroreflective cube-cornerelements; d) a second film having a first side and a second side; and e)a second array of retroreflective cube-corner elements attached to thefirst side of the second film, the second array of retroreflectivecube-corner elements being attached to the second side of the firstfilm.
 42. The retroreflective structure of claim 41 further comprising abacking layer attached to the first array of retroreflective cube-cornerelements.
 43. The retroreflective structure of claim 41 wherein at leastsome of the cube-corner elements of the second array cover the at leastsome of the apertures such that the at least some of the cube-cornerelements are air-backed.
 44. The retroreflective structure of claim 41wherein the second array of retroreflective cube-corner elements isattached to the second side of the first film by a substantially clearadhesive.